Basic Chemistry for Anatomy & Physiology

Basic Chemistry

Introduction

This section provides foundational chemistry concepts essential for understanding Anatomy & Physiology. It covers matter, energy, atomic structure, chemical bonds, and the types of chemical reactions relevant to biological systems.

Matter and Energy

Definitions and Properties

• Matter: Anything that has mass and occupies space. Matter can be seen, smelled, and/or felt.

• Weight: The effect of gravity on mass.

States of Matter

• Solid: Definite shape and volume.

• Liquid: Changeable shape, definite volume.

• Gas: Changeable shape and volume.

Energy

• Energy: The capacity to do work or put matter into motion. Energy has no mass and does not take up space.

• Forms of Energy:

  • Kinetic Energy: Energy in action (e.g., movement).

  • Potential Energy: Stored energy (e.g., in chemical bonds).

• Types of Energy in the Body:

  • Chemical Energy: Stored in bonds of chemical substances.

  • Electrical Energy: Results from movement of charged particles.

  • Mechanical Energy: Directly involved in moving matter.

  • Radiant/Electromagnetic Energy: Travels in waves (e.g., light).

Energy Conversions

• Energy can be converted from one form to another (e.g., chemical energy in food converted to mechanical energy for movement).

• Some energy is always lost as heat during conversions.

Atoms and Elements

Definitions

• Element: A substance that cannot be broken down into simpler substances by ordinary chemical methods.

• Atom: The smallest particle of an element that retains its properties.

Major Elements of the Human Body

• Four elements make up about 96% of body mass:

  • Oxygen (O)

  • Carbon (C)

  • Hydrogen (H)

  • Nitrogen (N)

• Other elements are present in smaller amounts (trace elements).

Atomic Structure

• Atoms are composed of subatomic particles:

  • Protons: Positive charge, located in nucleus, mass = 1 amu.

  • Neutrons: No charge, located in nucleus, mass = 1 amu.

  • Electrons: Negative charge, orbit nucleus, negligible mass.

• The number of protons equals the number of electrons in a neutral atom.

Identifying Elements

• Atomic Number: Number of protons in the nucleus.

• Mass Number: Total number of protons and neutrons.

• Isotopes: Atoms with the same number of protons but different numbers of neutrons.

• Atomic Weight: Average of mass numbers of all isotopes of an element.

Radioisotopes

• Unstable isotopes that decompose to more stable forms, emitting radiation.

• Used in medical diagnosis and treatment (e.g., Iodine-123 for thyroid scans).

• Can cause tissue damage (e.g., from uranium decay).

Combining Matter: Molecules, Compounds, and Mixtures

Molecules and Compounds

• Molecule: Two or more atoms bonded together (e.g., O2).

• Compound: Molecule with two or more different kinds of atoms bonded together (e.g., H2O).

Mixtures

• Physical combinations of two or more components.

• Three main types:

  1. Solutions: Homogeneous mixtures; solute particles are very tiny and do not settle out or scatter light (e.g., saline solution).

  2. Colloids: Heterogeneous mixtures; solute particles are larger than in solutions and scatter light, but do not settle out (e.g., cytosol).

  3. Suspensions: Heterogeneous mixtures; solute particles are very large, settle out, and may scatter light (e.g., blood).

Concentration of Solutions

• Expressed as:

  • Percent (parts solute per 100 parts solvent)

  • Milligrams per deciliter (mg/dL)

  • Molarity (moles of solute per liter of solution)

• Avogadro's Number: $6.02 \times 10^{23}$ molecules per mole.

Chemical Bonds

Types of Chemical Bonds

• Ionic Bonds: Formed by transfer of electrons from one atom to another, resulting in ions (cations and anions). Attraction of opposite charges forms the bond.

• Covalent Bonds: Formed by sharing of two or more valence electrons between atoms. Can be nonpolar (equal sharing) or polar (unequal sharing).

• Hydrogen Bonds: Weak attractions between a hydrogen atom (already covalently bonded to another atom) and an electronegative atom. Important in water and biological molecules.

Role of Electrons in Chemical Bonding

• Electrons in the outermost shell (valence shell) are involved in chemical bonding.

• Octet rule: Atoms tend to gain, lose, or share electrons to achieve 8 electrons in their valence shell.

Chemical Reactions

Types of Chemical Reactions

• Synthesis (Combination) Reactions: Atoms or molecules combine to form a larger, more complex molecule. Used in anabolic (building) processes.

• Decomposition Reactions: Molecule is broken down into smaller molecules or atoms. Used in catabolic (breaking down) processes.

• Exchange (Displacement) Reactions: Involve both synthesis and decomposition; bonds are made and broken.

Redox (Oxidation-Reduction) Reactions

• Atoms are reduced when they gain electrons and oxidized when they lose electrons.

Energy Flow in Chemical Reactions

• Exergonic Reactions: Release energy (products have less potential energy than reactants).

• Endergonic Reactions: Absorb energy (products have more potential energy than reactants).

Summary Table: Types of Chemical Bonds

Bond Type	How Formed	Example	Strength
Ionic	Transfer of electrons	NaCl (table salt)	Moderate
Covalent	Sharing of electrons	H2O (water)	Strong
Hydrogen	Attraction between H and electronegative atom	Between water molecules	Weak

Additional info:

• Atomic and molecular structure is foundational for understanding physiological processes such as nerve conduction, muscle contraction, and metabolism.

• Understanding chemical reactions is essential for grasping metabolic pathways and energy production in cells.